Antibody-Mediated Screening of Peptide Inhibitors for Monoamine Oxidase-B (MAO-B) from an Autodisplayed F-V Library

ABSTRACT: Inhibitors for monoamine oxidase-B (MAO-B) were screened froman FVlibrary with a randomized complementarity-determining region 3 (CDR3)region using a monoclonal antibody against dopamine. As thefirst step, the FVlibrary was expressed on the outer membrane ofE. coliby site-directed mutagenesisof the randomized CDR3 region. Among the FVlibrary, variants with a bindingaffinity to monoclonal antibodies against dopamine were screened and cloned.From the comparison of the binding activity of the screened clones to a controlclone with a modified FVantibody (only with CDR1 and CDR2), the CDR3regions of screened clones were determined to directly interact with the monoclonalantibody against dopamine. These CDR3 sequences were then synthesized asmimotopes (mimicking peptides) of dopamine. The inhibitory activity of twomimotopes against MAO-B was analyzed using HeLa cells overexpressing MAO-B,as well as using activated human astrocytes; their inhibitory activity was comparedto that of a commercial inhibitor of MAO-B, selegiline. The inhibition efficiency ofthe two mimotopes (in comparison with selegiline) was estimated to be 67.2% and 69.4% in the HeLa cells and 64.4% and 58.0% inthe human astrocytes. The gene expression pattern in astrocytes after treatment with the two mimotopes was also analyzed andcompared with that in the human astrocytes treated with selegiline. Finally, the interaction between two mimotopes and MAO-B wasanalyzed using docking simulation, and the candidate regions of MAO-B for the interaction with each mimotope were exploredthrough the docking simulation.

DOI: https://doi.org/10.1021/acs.bioconjchem.2c00107